DEAR DR. BLONZ: I enjoy seafood of all types, but I am concerned that some are high in cholesterol. One of the attractions of seafood is that it is generally low in saturated fat, and heart disease runs in my family. How concerned should I be about the high cholesterol levels in some kinds of seafood? -- S.L., San Diego
DEAR S.L.: Animal-derived foods do contain cholesterol; most seafood contains about the same amount as skinless poultry and other sources of lean meat. The most notable exceptions are shellfish, which include crustaceans (shrimp, crab and lobster) and mollusks (clams, oysters, mussels, octopus and scallops).
Shellfish are great sources of low-fat, high-quality protein, but they contain compounds called sterols that are in the same family as cholesterol. Older analytical methods lumped these sterols together with cholesterol, resulting in shellfish being pegged as high-cholesterol foods. Newer testing methods uncovered the oversight. We now know that shellfish have more cholesterol than other fish, but they are not as rich in cholesterol as was once thought. It was also discovered that the non-cholesterol sterols in shellfish can play a role in inhibiting the absorption of the dietary cholesterol that is present.
The connection between dietary cholesterol, blood cholesterol and heart disease is not always clear. Every milligram of cholesterol in our foods does not end up cruising around the bloodstream looking for trouble. Most of the cholesterol in the bloodstream, it turns out, is manufactured by the liver as needed. When cholesterol is absorbed from food, the liver is programmed to make less.
In some people, however, this coordination malfunctions. (Blood tests know as lipid profiles can help reveal this -- another reason to be screened periodically.) Such individuals have to pay closer attention to the type and level of fat and cholesterol in their diets. Lifestyle can also play a role. One problematic nutrient in this scenario is excess sugar. Too much sugar will contribute to a range of health problems, as well as elevated triglycerides and cholesterol.
Fish, especially fatty fish such as salmon, sardines and anchovies, are good sources of healthful long-chain omega-3 fats (EPA and DHA). Assuming there are no allergies or other restrictions, seafood -- including shellfish -- is a healthful category of foods to include in your diet.
DEAR DR. BLONZ: How much does pressure-cooking vegetables deplete their vitamins and minerals? -- S.B., Chicago
DEAR S.B.: Cooking and storing foods can deplete nutrients, to some degree. The actual nutrient losses during cooking depend on several factors, including temperature, cooking time, type of food, size of the food pieces and amount of water used, if any. The amount of loss will vary with the nutrient.
Water can dilute and deplete some of the water-soluble vitamins if the cooking water is discarded. Heat, regardless of its source, can affect fat-soluble vitamins. Because cooking in a pressure cooker typically uses less water and shorter cooking times, more water-soluble nutrients remain.
The most cooking-stable of the nutrients are the minerals. Unless a relatively large amount of water is used and discarded when preparing foods with small particle sizes, most minerals tend to end up on the plate.
Send questions to: “On Nutrition,” Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to email@example.com. Due to the volume of mail, personal replies cannot be provided.